Fuel pump for gasoline engines



Dec. 18, 1934. G. R, WELCH 1 FUEL PUMP FOR GASOL-INE ENGINES Filed July 10, 1933 Wwf INVENTOR. Gio/Pcf /Q Nac/n ATTORNEY.

Patented Dec. 18, 1934 UNITED STATES PATENT OFFICE 1Claim.

This case is based upon my abandoned application Serial No. 628,401, led August I11, 1932.

The invention refers to that type of fuel pump in which a piston having a variable stroke is caused to vary its stroke in proportion to the variable demand.

The object of this invention is to eliminate the leakage which is apt to occur around the edges of a piston. This leakage is taken care of in this type of fuel pump by means of a groove inthe cylinder Walls which is intermittently connected with the cylinder thru a check valve so that whenever the piston takes a suction stroke it automatically sucks any fuel that has leaked past the piston into the groove back into the cylinder. It is obvious that with this construction, so long as the piston is actively reciprocating, the pump will automatically absorb any fuel that leaks into lthe groove and the tendency will be to draw in a little air thru the piston into the groove so that the piston will operate dry.

The problem to be solved, therefore, was to prevent the pump leaking when the piston was not pumping fuel activelythat is-when the demand approached zero. To prevent leakage at such a minimum discharge, I discovered, by simply providing a restricted leak near to or thru the inlet choke valveof the pump, I could make sure that the piston was displaced at all times, even when there was no demand and, therefore, no discharge from the pump. The reason for this is that the piston was forced to make good at each positive stroke, the discharge lost by the leakage `thru the check valve back into the suction line between each positive stroke. Another problem to be solved was to get rid o f the pressuTe remaining in the cylinder of the pump after the engine stops as quickly as possible. The few seconds this residual pressure remains in the cylinder encourages leakage. The constant leak referred to provides a restricted passage thru which the pressure is instantaneously relieved.

A minor problem was the elimination of noise. The invention relates to pumps particularly designed for use in the feeding of fuel to internal combustion engines and it is the object of the invention first, to obtain a construction which is efficient in its operation under various conditions incident to its use; second, to obtain a simple construction which may be manufactured at low cost and is easily assembled and installed. With these and other objects in view the invention consists in the construction as hereinafter Set forth.

(Cl. ID3-153) In the drawing:

Figure 1 is a vertical central longitudinal section through my improved fuel pump;

Figure 2 is a plan view thereof partly broken awa;r in the plans of the inlet;

Figure 3 is a side elevation partly in section;

Figure 4 is a horizontal section substantially on line 4 4 of Figure 1.

Figure 5 is a diagrammatic illustration showing the principle of operation.

My improved pump is designed for installation upon the crank case of an internal combustion engine in such position as to be in operative relation with a moving part of the engine, such for instance as the cam shaft.

Preferably, the unit is mounted upon a top or side wall of the crank case which is apertured for extension therein of the plunger which is either directly or indirectly engaged with the cam shaft or other moving part. As shown, A is a housing provided at its lower end with a flange B for bolting or otherwise attaching to the crank case and having in its lower portion a cylindrical bore C which forms the pump barrel. D and E are bores in the upper portion of the casing A for receiving seats F and F' for check valves G and G. The small hole G", possibly #58 hole, is provided in the check valve G for the purpose described. The bore D intersects a cross bore H forming the fuel inlet passage andq which contains a screen I for excluding sediment from access to the valve seat or the barrel of the pump. 'I'he bore E is connected with an outlet conduit (not shown) which leads to the point of discharge for the fuel. Both bores D and E are closed by screw threaded caps J and the bore D is connected above the Valve G by a passage K with a central upward extension L of the pump barrel while the bore E is connectedvbelow the valve with the pump barrel. The caps J are provided with pintles M around which are sleeved springs N which yieldingly hold the valves G and G'to their seats.

Within the pump barrel C is arranged a piston O preferably formed of cupped sheet metal. Centrally within the piston is an operating plunger P provided with a lost motion connection thereto, preferably of the following construction. Within the cupper piston O is an inner cup member Q secured therein by` an inturned flange O at the lower end of the cup O. The member Q has its upper end reversely cupped at Q to leave a clearance space between its bottom and the end of the cup 0. Centrally within the bottom of the re- Verse cup Q' is an aperture R for receiving the ycomparatively high vapor content.

upper end .of the plunger P which latter is provided'with an enlarged head P'. The cup Q is cut away at R. in its bottom and at one side to form an entrance slot for the head P' so that the latter may be engaged with the piston O by first entering through the slot R' and then engaging it with the central aperture R. The plunger P is normally held centered within the cup O by a guide bearing S which is carried by a threaded cap member S' engaged with a correspondingly threaded aperture in the lower end of the pump barrel. T is a coil spring surrounding the reverse cup Q' within the cup Q and having its opposite end abutting against the cap S'. U is a second spring` of greater tension than the spring T which surrounds the plunger P in the portion thereof external to the pump barrel engaging a head or flange l5'2 on said plunger and having its opposite end abutting against the cap S.

With the parts constructed as thus far described they may be assembled in the following manner. The plunger P has rst sleeved therein the spring U and is then engaged with the guide bearing, S. The spring T is then placed within the cups Q and O and sleeved over the guide bearing S. By then compressing the spring T and tilting the cups Q and O atan angle, the head P of the plunger may be engaged with the entrance slot R' so as to be above the bottom of the reverse cup Q'. Following this the cups O and Q are inserted within'the pump barrel Cand the cap S is screwed into engagement with the casing A.

As thus assembled, the springs T and U will be in opposition to each other, the former tending to raise the cupped piston and the latter acting through the medium of the plunger P tending to draw it downward. Inasmuch, however, as the spring U is of greater tension, the piston O is normally held downward so as to leave a clearance space between its upper end and the upper end of the barrel C.

In operation, whenever the plunger P is lifted by any mechanism such as an eccentric on a cam shaft of the` engine and any suitable intermediate mechanism (not shown) between the same and said plunger P, the spring T will lift the cupped piston displacing any fluid in the pump barrel above the same and forcing it outward beyond the valve G' through the discharge conduit. On the other hand, when the plunger Pix is moved downward by the withdrawal of the eccentric and the excess tension of the spring U. the head P' of the plunger will draw the reverse cup Q downward and through the medi-um of this and the cup Q will move downward the piston O.

lThis will draw fluidfrom the inlet past the check valve G and through the port K and passage L into the pump barrel C. It will be noted, however, that there is no positive connection between the plunger P and the piston O which will force the latter 'in an upward direction and that the .raising of the piston is eil'ected solely by the operation of the spring T. As this spring is oi' a predetermined tension, this will determine the maximum pressure that can be brought to bear upon the uid 'in the pump barrel and consequently it will be impossible for the-pump to ydevelop any pressure above this limit.

Some of the problems that are encountered in the operation of a pump of this character are as follows: When the engine is in operation the crank case will be filled with warm air having a If then the engine remains idle in cold weather condensation of the vapor will occur on the metal parts including the plunger P and spring U which project into the crank case. In freezing weather this condensation will turn to ice and by accumulation will eventually build up around the metallic parts. Thus if relatively moving parts 'were in close proximity to each other, the one might freeze to the other so as to render the pump inoperative. However, with my construction the space provided between the spring U and the plunger is such as to preclude any such freezing up.

Ice may also form by freezing of water which is held in suspension in the fuel. This will tend to collect on the top of the piston but the clearance within the barrel is suicient so that under ordinary circumstances the amount of ice thus accumulated will not interfere with the operation of the pump. In case, however, that the piston O is prevented from movement in the barrel, the plunger P isfree to move without the application of destructiveforce upon any parts of the mechanism.

A certain amount of leakage is sure to occur between the piston and the wall of the barrel. This leakage is slight but if allowed t'o accumulate would eventually fill the space below the piston and prevent operation of the pump. I have guarded against such result by providing a clearance channel W surrounding the barrel in the central portion thereof intowhich any leakage from above will accumulate. This channel is connected to a by-pass X containing a check valve X by which fuel in said channel may be returned to the chamber above the piston. The force for thus returning the fuel would be furnished by the higher air` pressure in the pump barrel below the piston when the latter moves downward. This by-pass and check valve may be arranged at one side of the casing as shown in Figure 3, the valve being a ball and normally held to its seat by a weight X2.

When the pump is standing idle, there is a possibility of a slight leakage of the liquid fuel past the piston, which in time would accumulate in the bottom of the cylinder and might eventually find its way into the crank case. To guard against this I have provided a bleed port Y through the wall of the casing at the lower end of the pump barrel. This will permit the escape of any liquid fuel in the bottom of the barrel but is so restricted in area that when the pump is in operation, a greater than atmospheric pressure will be developed in the lower portion of the barrel upon the descent of the piston, thereby facilitating the return of the fuel through the by-pass. In order that thefpiston shall operate at all times, even when the demand is zero, a small hole G" is provided thru the check valve G.

One matter of importance is the reduction of noise of operation to the minimum. Inasmuch as the plunger P )is non-positively connected with the piston, there might be a tendency for the development of noise whenever the head P' is separated from its bearing on the reverse cup Q'. I have avoided such result by forming the seat for the head P' of a resiliently yieldable member.

This is accomplished by radially slotting the bottom of the reverse cup Q as indicated at Z to form resilient segments Z therebetween which diretly engage the head P. -Thus there will be little tendency for the head P to separate from the segment Z in the normal operation of the .pump and even where there is such separation the resilient character of said segments will prevent objectionable noise when the head P' strikes thereagainst.

By constructing the piston of an outer shell O and an inner shell Q spun into at O' the resonance of the one piece piston is eliminated so that the impact of the head P' striking Q will not produce objectionable noises.

The construction as above described is therefore one which is adapted to remain operative under the varying conditions incident to its use on an internal combustion engine and as previously stated,.is so simple and has so few parts as to be capable of manufacture at low cost.

What I claim is:

In a fuel pump having a cylinder and a piston adapted to reciprocate therein with a stroke that varies automatically with the demand, an inlet passage leading to said cylinder, a check valve therein, means for preventing leakage past the piston comprising a groove in the cylinder walls covered at all times by the piston, a passage leading from said groove to the interior of said cylinder, a second check valve in said passage, a restricted return bypass formed around said irst `check valve leading from the cylinderl back into 10 said inlet passage.

GEORGE R. WELQH. 

